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| United States Patent |
5,214,272
|
|
Ueno
|
May 25, 1993
|
Photoelectric converting apparatus
Abstract
A photoelectric converting apparatus has a plurality of photoelectric
converting devices each of which can execute a photoelectric conversion
and is constructed so that photo carriers can be accumulated onto a
control electrode. At least one of the photoelectric converting devices is
covered by a conductive light shielding layer. A transparent electrode is
formed on at least the other photoelectric converting devices.
| Inventors:
|
Ueno; Isamu (Atsugi, JP)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
738564 |
| Filed:
|
July 31, 1991 |
Foreign Application Priority Data
| Aug 02, 1990[JP] | 2-203967 |
| Jul 26, 1991[JP] | 3-208804 |
| Current U.S. Class: |
250/208.1; 250/578.1; 257/435; 257/E27.149; 348/243 |
| Intern'l Class: |
H01J 040/14 |
| Field of Search: |
250/208.1,578.1
357/30 L
358/213.16
257/435
|
References Cited
U.S. Patent Documents
| 4293877 | Oct., 1981 | Tsunekawa et al. | 357/30.
|
| 4484223 | Nov., 1984 | Tsunekawa | 358/213.
|
| 4672221 | Jun., 1987 | Saito et al. | 357/30.
|
| 4678938 | Jul., 1987 | Nakamura | 250/208.
|
| 4879470 | Nov., 1989 | Sugawa et al. | 250/578.
|
| 4939592 | Jul., 1990 | Saika et al. | 250/208.
|
| 5159186 | Oct., 1992 | Ohzu | 250/208.
|
| Foreign Patent Documents |
| 38474 | Oct., 1981 | EP.
| |
Other References
"A Low-Noise Bi-CMOS Linear Image Sensor with Auto-Focusing Function", IEEE
Transactions on Electron Devices, vol. 36, No. 1, pp. 39 and 42.
|
Primary Examiner: Hannaher; Constantine
Assistant Examiner: Glick; Edward J.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Claims
What is claimed is:
1. A photoelectric converting apparatus comprising a plurality of
photoelectric converting devices each having a respective control
electrode and a photoreceiving region responsive to light incident thereon
and capable of storing photocarriers produced by the light incident
thereon for producing an electric output corresponding to the incident
light according to the number of stored photocarriers, wherein a
conductive light shielding layer is provided on said photoreceiving region
of at least one of said photoelectric conversion devices and spaced by an
insulating layer from said photoreceiving region of said at least one said
photoelectric conversion devices, and a transparent conductive layer is
provided on and spaced by an insulating layer from said photoreceiving
region of another of said photoelectric conversion devices.
2. An apparatus according to claim 1, wherein shapes of the light shielding
layer and the transparent conductive layer are identical or substantially
identical.
3. An apparatus according to claim 1, wherein a boundary region to
electrically separate the photoelectric converting devices is formed
between the photoelectric converting devices.
4. An apparatus according to claim 3, wherein the light shielding layer is
formed on the boundary region.
5. An apparatus according to claim 1, further having a region in which the
light shielding layer and the transparent conductive layer are laminated.
6. An apparatus according to claim 1, wherein the transparent conductive
layer is formed by at least one material which is selected from the group
consisting of indium tin oxide, indium oxide, tin oxide, zinc oxide,
cadmium oxide, cadmium tin oxide, titanium oxide, and thin metal film.
7. An apparatus according to claim 1, wherein the light shielding layer is
made of Al and/or an Al alloy.
8. An apparatus according to claim 7, wherein said Al alloy is at least one
alloy which is selected from the group consisting of Al-Si, Al-Ti, Al-Cu,
Al-Si-Ti, and Al-Si-Cu.
9. An apparatus according to claim 1, wherein the control electrode is a
base region.
10. A photoelectric conversion apparatus comprising:
a photoelectric conversion device for light pixel, having a control
electrode constituted for storing a photocarrier produced by light
incident on a photoreceiving section, wherein a transparent electrode is
provided on said photoreceiving section of said photoelectric conversion
device for light pixel;
a photoelectric conversion device for dark pixel having a control
electrode, having the same or substantially the same structure as said
photoelectric conversion device for light pixel, wherein a conductive
light shielding layer to be used as an electrode covers at least a section
of said photoelectric conversion device for dark pixel corresponding to
the photoreceiving section of said photoelectric conversion device for
light pixel; and
a dark output compensation section for subtracting an output from said
photoelectric conversion device for dark pixel from an output from said
photoelectric conversion device for light pixel, for producing a
photoelectric conversion output.
11. An apparatus according to claim 10, wherein said light shielding layer
and said transparent electrode are provided correspondingly to said
control electrode.
12. An apparatus according to claim 10, wherein said light shielding layer
and said transparent electrode have the same or substantially the same
configuration.
13. An apparatus according to claim 10, further comprising a boundary
region provided between said photoelectric conversion devices for
electrically isolating said photoelectric conversion devices from each
other.
14. An apparatus according to claim 13, wherein said light shielding layer
is provided on said boundary region.
15. An apparatus according to claim 10, wherein said light shielding layer
and said transparent electrode overlap with each other.
16. An apparatus according to claim 10, further comprising an insulating
layer provided between said control electrode and said light shielding
layer.
17. An apparatus according to claim 10, further comprising an insulating
layer provided between said transparent electrode and said control
electrode.
18. An apparatus according to claim 10, wherein said transparent electrode
is formed of at least one of materials selected from the group consisting
of indium tin oxide, indium oxide, tin oxide, zinc oxide, cadmium oxide,
cadmium tin oxide, titanium oxide, and thin metal film.
19. An apparatus according to claim 10, wherein said light shielding layer
is formed of a material selected from the group consisting of Al or Al
alloy.
20. An apparatus according to claim 19, wherein said Al alloy comprising at
least one metal selected from the groups consisting of Al-Si, Al-Cu,
Al-Si-Ti, and Al-Si-Cu.
21. An apparatus according to claim 10, wherein said control electrode is a
base region.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric converting apparatus and,
more particularly, to a photoelectric converting apparatus having a
plurality of photoelectric converting devices each of which can accumulate
photocarriers onto a control electrode and can execute a photoelectric
conversion and having at least a part of the photoelectric converting
devices.
2. Related Background Art
As a photoelectric converting apparatus, there has been known an apparatus
in which a light shielding layer is formed on a plurality of photoelectric
converting devices formed on a semiconductor substrate so as to cover at
least a part of the photoelectric converting elements and such a
photoelectric converting device which has been covered by the light
shielding layer is allowed to act as a dark pixel (for instance, U.S. Pat.
No. 4,879,470).
A dark output compensation will now be briefly explained hereinbelow. FIG.
1A is a schematic constructional diagram of a conventional photoelectric
converting apparatus having a dark output compensating function.
In the diagram, a sensor section 701 comprises: cells 7S.sub.1 to 7S.sub.n
of an opening portion to execute a photoelectric conversion; and a cell
7S.sub.d of a light shielding portion to obtain a dark reference output.
Signals of the cells are sequentially generated by a scan section 702 and
are supplied to a dark output compensation section 703. The dark output
compensation section 703 subtracts the dark reference signal component of
the cell 7S.sub.d from the signals of the cells 7S.sub.1 to 7S.sub.n and
generates a resultant output signal.
Since an output of the sensor cell 7S.sub.d of the light shielding portion
corresponds to a dark current of the sensor cell, by subtracting the dark
reference signal component of the cell 7S.sub.d from the signals of the
cells 7S.sub.1 to 7S.sub.n, a noise component by the dark current is
eliminated. Consequently, a photoelectric conversion signal which
accurately corresponds to incident light can be obtained.
As a dark output compensation section 703, a clamping circuit can be used
or a sample and hold circuit to keep the dark reference signal of the cell
7S.sub.d and a differential circuit to calculate differences between the
dark reference signal and the signals of the cells 7S.sub.1 to 7S.sub.n
can be also used.
Explanation will now be made with reference to FIG. 1B which
diagrammatically shows one pixel of photoelectric converting devices of
the type which accumulates photocarriers onto a control electrode of a
semiconductor transistor. Each of the photoelectric converting devices is
constructed on a buried layer 26 formed on a semiconductor substrate 27
and comprises epitaxial layers 24, base layers 25, and device separating
layers 23. A transparent insulating layer 22 is formed over each of the
photoelectric converting devices. Further, the photoelectric converting
device which functions as a dark pixel is covered by a metal light
shielding layer 21 formed in or on the insulating layer 22.
There is a case where the photoelectric converting device having the light
shielding layer which has been provided in correspondence thereto is
hereinafter called a dark pixel and the photoelectric converting device to
which a photosignal or optical information can enter is called a light
pixel.
In the conventional photoelectric converting apparatus as shown in FIG. 1B,
there are many cases where the light shielding layer 21 is also used as a
power source line of V.sub.cc or the like. Therefore, a parasitic capacity
is formed between the light shielding layer and the base region and a
difference occurs between the base capacities of the dark pixel and the
light pixel. Such a phenomenon will be described by using an equivalent
circuit (FIG. 2) of a linear sensor in which BASIS (Base Store Image
Sensor) are one-dimensionally arranged and a timing chart (FIG. 3) when
such a linear sensor operates.
When a clock .phi..sub.CR rises at time t.sub.1, transistors M.sub.41 to
M.sub.4n are simultaneously turned on and all of temporary accumulation
capacitors C.sub.1 to C.sub.n are reset to VCR. When a clock .phi..sub.T
rises at time t.sub.2, transistors M.sub.31 to M.sub.3n are turned on,
transistors Q.sub.1 to Q.sub.n of a sensor section are turned on, and
photo-signals accumulated in base capacitors Cb.sub.1 to Cb.sub.n are read
out to the capacitors C.sub.1 to C.sub.n, respectively. After that, a
clock .phi..sub.BR trails at time t.sub.3, transistors M.sub.11 to
M.sub.1n are turned on, and the bases of the sensor section are reset
(complete reset). Further, at time t.sub.4, a clock .phi..sub.ER rises,
transistors M.sub.21 to M.sub.2n are turned on, emitters of the
transistors Q.sub.1 to Q.sub.n are reset to VER, and the sensor is
transiently reset.
After completion of the reading into the temporary accumulation capacitors
and resetting of the sensor, the sensor starts the accumulating operation
and the accumulated signals are read out of the temporary accumulation
capacitors to an output terminal V.sub.out. That is, when a clock
.phi..sub.HR rises at time t.sub.5 and a transistor M.sub.6 is turned on,
an output line L is reset. When an output SR.sub.1 from a shift register
SR rises at time t.sub.6, a transistor M.sub.51 is turned on and the
signal is read out of the capacitor C.sub.1 to the output line. By
repeating such a reading operation only the a number of times equal to the
number of pixels, the reading operations are completed.
When considering the nth pixel in the reading operation from the sensor to
the temporary accumulation capacitor, assuming that a long enough reading
time has been given, an output voltage VE at the emitter terminal of the
transistor Q.sub.n is expressed as follows:
##EQU1##
where, A: pixel area
i.sub.p : photo current density
t.sub.s : accumulation time
Cb.sub.n : temporary accumulation capacity of the nth pixel
Therefore, as mentioned above, if temporary accumulation capacities Cb of
the dark pixel and the light pixel differ, an output of the dark pixel
differs from an output in, the dark state., of the light pixel, so that
there is there occurs the case where a problem that the output of the dark
pixel cannot be used as a black reference.
FIG. 4 shows a photoelectric converting apparatus in which pixels are
two-dimensionally arranged. Reference numeral 101 denotes a vertical
driving line; 102 a vertical scanning circuit; 103 a vertical signal line;
104 a switch means; 105 a horizontal signal line; 106 a horizontal
scanning circuit; 107 buffer means; 108 horizontal signal line resetting
means; and 110 a light shielding layer. Even in the photoelectric
converting apparatus with the above structure, in the case where dark
pixels are arranged like S.sub.11 to S.sub.1n, each base capacity of the
dark pixels S.sub.11 to S.sub.1n is large and differs from a base capacity
of the light pixel, so that the same problem as in the linear sensor
occurs.
SUMMARY OF THE INVENTION
The invention is made to solve the problems in the conventional
photoelectric converting apparatus as mentioned above, and it is an object
of the invention to provide a photoelectric covnerting apparatus in which
a light pixel and a dark pixel have equal temporary accumulation capacity
and a stable dark pixel output can be obtained as a black reference.
Another object of the invention is to provide a photoelectric converting
apparatus having a plurality of photoelectric converting devices each of
which can execute a photoelectric conversion and is constructed so that
photocarriers can be accumulated onto a control electrode, wherein at
least one of the photoelectric converting devices is covered by a
conductive light shielding layer and a transparent electrode is formed on
at least the other photoelectric converting devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a diagrammatical constructional view of a photoelectric
converting apparatus for describing a dark output compensation;
FIG. 1B is a vertical sectional view showing one pixel of each of a dark
pixel and a light pixel of a conventional photoelectric converting
apparatus;
FIG. 2 is an equivalent circuit diagram of a linear sensor in which
photoelectric converting apparatuses of FIG. 1B are arranged like a plane;
FIG. 3 is an operation timing chart of the circuit of FIG. 2;
FIG. 4 is an equivalent circuit diagram of a sensor in which pixels are
two-dimensionally arranged;
FIG. 5 is a vertical sectional view showing a dark pixel and a light pixel
of a photoelectric converting apparatus according to an embodiment of the
invention;
FIGS. 6 and 7 are vertical sectional views showing photoelectric converting
apparatuses according to other embodiments of the invention and are
diagrams similar to FIG. 5;
FIGS. 8A to 8F are explanatory diagrams showing steps of manufacturing the
photoelectric converting apparatus of FIG. 6; and
FIGS. 9 to 17 are variously circuit diagrams or sectional views of
photoelectric converting apparatuses according to other embodiments of the
invention, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention intends to provide a photoelectric converting apparatus
having photoelectric converting devices in which a light shielding layer
made of a conductive material is provided in order to shield the light
which enters a photosensitive surface of a pixel which acts as a dark
pixel, wherein a transparent electrode having the same or substantially
the same shape as that of the light shielding layer is arranged, at a
position in front of the photosensitive surface of a pixel which acts as a
light pixel. Thus, substantially the same condition with respect to the
foregoing parameters which exert an influence on output voltages of the
dark pixel and the light pixel is given to the dark and light pixels, so
that a stable dark output can be obtained.
An embodiment of the invention will be described hereinbelow with reference
to the drawings. FIG. 5 shows one pixel which acts as a dark pixel D and
one pixel which acts as a light pixel L in a photoelectric converting
apparatus having a plurality of pixels. Reference numeral 1 denotes a
light shielding layer; 2 an insulating layer; 3 a device separating region
of an n.sup.+ semiconductor region; 4 an epitaxial region of an n.sup.-
semiconductor region; 5 a base region as a control electrode; 6 a buried
layer of the n.sup.+ semiconductor region; 7 a semiconductor substrate;
and 10 a transparent electrode. The insulating layer 2 is transparent or
substantially transparent. The light shielding layer 1 is provided within
part of the insulating layer 2 in order to use the pixel covered by the
light shielding layer as a dark pixel. The light shielding layer 1 has a
large area enough to cover the photo sensitive surface of the
photoelectric converting device. The transparent electrode 10 has the same
or substantially the same structure as that of the light shielding layer 1
except that the electrode 10 is transparent.
As a material of the transparent electrode 10, it is possible to preferably
use at least one material which is selected from the group consisting of
indium tin oxide (ITO), indium oxide, tin oxide, zinc oxide, cadmium
oxide, cadmium tin oxide, titanium oxide, and Au thin film.
In the photoelectric converting apparatus constructed as mentioned above,
as will be obviously understood by comparing with the conventional
photoelectric converting apparatus shown in FIG. 1B, the portion of the
dark pixel D and the portion of the light pixel L have substantially
electrically the same structure with respect to a point that the
conductive layer is located over the base region 5 through the insulating
layer 2. Therefore, the parameters in the equation (1) are substantially
equal with regard to the portion of the dark pixel D and the portion of
the light pixel L. The output of the dark pixel can be used as an accurate
black reference.
FIG. 6 shows another embodiment of the invention. In this embodiment, the
light shielding layer 1 has: a first portion 11 having a large area enough
to cover the photosensitive surface of the pixel; and a second portion 12
which extends downward from an edge portion of the first portion 11. The
first portion 11 extends along the surface of the insulating layer 2. The
second portion 12 penetrates the insulating layer 2 in the thickness
direction and reaches the surface of the device separating region 3.
Similarly, the transparent electrode 10 has a first portion 13 and a
second portion 14 which extends downward from an edge portion of the first
portion 13. According to this embodiment, the upper region of the
photosensitive surface of the pixel which acts as a dark pixel is covered
by the first portion 11 at an upper position and is covered by the second
portion 12 at a side position, respectively. Therefore, the light which
has entered the sensor surface perpendicularly, or at an angle near a
right angle, is almost completely shielded by the first portion 11 of the
light shielding layer 1. The light which has obliquely entered the sensor
surface is shielded by the second portion 12 which starts from the edge
portion 12 of the first portion 11 and reaches the surface of the device
separating region 3. By using the above structure, a situation such that
the light unexpectedly enters the photo sensitive surface is eliminated
and the pixel covered by the light shielding layer can be allowed to
further stably function as a dark pixel.
FIG. 7 shows another embodiment of the invention. A photoelectric
converting apparatus of this embodiment has a structure such that a light
shielding layer 8 locating in the device separating region 3 is further
provided for the photoelectric converting apparatus shown in FIG. 6.
According to the above construction, a sufficient light shielding effect
is presented for not only the light which enters the insulating layer 2
from the side direction but also the light which enters the insulating
layer 2 from the side direction of the epitaxial layer 4, and so a further
high performance can be obtained as a dark pixel.
An example of steps of manufacturing the photoelectric converting apparatus
having the dark pixel of the structure shown in FIG. 2 will now be
described with reference to FIGS. 8A to 8F. First, a device structure
shown in FIG. 8A having the n.sup.+ type device separating region 3, the
n.sup.- type epitaxial region 4, the p type base region 5, and the
n.sup.+ type buried layer 6 is formed on the p type semiconductor
substrate 7. The insulating film 2 between layers made of phosphorus
glass, SiO.sub.2, or the like is deposited onto the epitaxial layer 4 by a
CVD method and holes 2a are formed in the inter-layer insulating film 2 by
patterning and etching (FIG. B). A conductive film is subsequently formed
by an ordinary method. The transparent electrode 10 as shown in FIG. 8C is
formed in the region corresponding to the light pixel by patterning.
Further, a resist film R is coated onto the transparent electrode 10 and
the insulating film 2. After that, a patterning is executed so as to form
holes R.sub.a in accordance with a predetermined pattern. Subsequently,
the insulating film 2 is etched and eliminated in the portions of the
holes R.sub.a. Thus, contact holes 2a as shown in FIG. 8D are formed.
After that, a conductive material having a light shielding performance is
evaporation deposited onto portions of desired regions excluding the
portion where the transparent electrode 10 has been formed, thereby
forming the light shielding layer 1 shown in FIG. 8E. The light shielding
layer 1 can be formed by using an Al-CVD method, which will be explained
hereinlater. Finally, the insulating layer 2 as a passivation film is
formed onto the light shielding layer 1 and the transparent electrode 10
by the CVD method (FIG. 8F).
The Al-CVD method which is applied to the manufacturing of the
photoelectric converting apparatus according to the embodiment of the
invention will now be described.
Film forming method
This method is suitable to bury a metal material into fine deep holes
(contact hole, through hole concave portion) in which, for instance, an
aspect ratio is equal to 1 or more and has an excellent selectivity. The
metal film formed by the above method has an extremely excellent
crystalline performance such that a monocrystalline aluminum is formed and
the metal film hardly contains carbon and the like.
Similarly, the above metal has a low resistivity within a range from 0.7 to
3.4 .mu..OMEGA..multidot.cm and a high reflectance within a range from 85
to 95% and has an excellent surface performance such that a density of
hillocks of 1 .mu.m or more lies within a range from about 1 to 100
cm.sup.-2.
With respect to a generation probability of alloy spikes at the interface
with silicon as well, a breakdown probability of a semiconductor junction
of 0.15 .mu.m is almost equal to 0.
According to the Al-CVD method, a deposition film is formed onto an
electron donative substrate by a surface reaction by using a gas of alkyl
aluminum hydride and a hydrogen gas. Particularly, monomethyl aluminum
hydride (MMAH) or dimethyl aluminum hydride (DMAH) is used as a raw
material gas and a H.sub.2 gas is used as a reaction gas and the surface
of the substrate is heated in the above mixture of gases, so that an Al
film of a good quality can be deposited.
When an Al film is selectively deposited, it is desirable to keep the
surface temperature of the substrate by direct or indirect heating to a
value which is equal to or higher than a decomposition temperature of
alkyl aluminum halide and lower than 450 .degree. C. More preferably, it
is desirable to keep the surface temperature within a range from 260
.degree. C. to 440 .degree. C.
As a method of heating the substrate within the above temperature range,
the direct heating method and the indirect heating method are known.
Particularly, by holding the substrate to the above temperature by the
direct heating method, an Al film of a good quality can be formed at a
high deposition speed. For instance, when the substrate surface
temperature upon formation of an Al film is set to a more preferable
temperature range from 260 .degree. C. to 440 .degree. C., a film of a
good quality is derived at a higher deposition speed than that in the case
of using a resistance heating method having a deposition speed of 3000
.ANG./minute. As such a direct heating method (an energy from the heating
means is directly transferred to the substrate and heats the substrate
itself), for instance, a lamp heating method using a halogen lamp, a xenon
lamp, or the like can be mentioned. On the other hand, as an indirect
heating method, there is a resistance heating method and such a method can
be realized by using a heat generating element provided for a substrate
supporting member arranged in a space to form a deposition film in order
to support a substrate on which a deposition film is to be formed.
By applying the CVD method to the substrate on which both of the electron
donative surface portion and the non-electron donative surface portion
exist by the above method, a monocrystal of Al is formed in only the
electron donative substrate surface portion at a good selectivity.
An electron donative material denotes a material such that free electrons
exist in the substrate or free electrons have purposely been produced and
which has the surface on which a chemical reaction is promoted by
transmission and reception of electrons between the substrate and raw
material gas molecules adhered on the substrate surface. For instance,
generally, metal or semiconductor corresponds to such a material. A
material such that a thin oxide film exists on the metal or semiconductor
surface can also cause a chemical reaction by the transmission and
reception of electrons between the substrate and the adhered raw material
molecules, so that the above material is also included in the electron
donative materials of the invention.
As practical examples of the electron donative materials, for instance,
there can be mentioned a III-V group compound semiconductors of a
multi-element system of the binary system, ternary system, or more which
are constructed by combining Ga, In, Al, or the like as an element of the
III group and P, As, N, or the like as an element of the V group, a
semiconductor material such as monocrystalline silicon, amorphous silicon,
or the like, or a material which is selected from the following metals,
alloys, silicides, and the like: for instance, tungsten, molybdenum,
tantalum, copper, titanium, aluminum, titanium aluminum, titanium nitride,
aluminum silicon copper, aluminum palladium, tungsten silicide, titanium
silicide, aluminum silicide, molybdenumm silicide, tantalum silicide, and
the like.
On the other hand, as materials which form the surface on whcih Al or Al-Si
is not selectively deposited, namely, as non-electron donative materials,
there can be mentioned silicon oxide formed by a thermal oxidation, CVD,
or the like, glass such as BSG, PSG, BPSG, or the like, an oxide film, a
thermal nitride film, and a silicon nitride film formed by a plasma CVD
method, a reduced pressure CVD method, an ECR-CVD method, or the like.
According to the Al-CVD method, the following metal films containing Al as
a main component can be also selectively deposited and qualities of such
metal films also exhibit excellent characteristics.
For instance, in addition to a gas of alkyl aluminum hydride and hydrogen,
a gas containing Si atoms of SiH.sub.4, Si.sub.2 H.sub.6, Si.sub.3 H.sub.8,
Si(CH.sub.3), SiCl.sub.4, SiOH.sub.2 CL.sub.2, SiHCl.sub.3, or the like,
a gas containing Ti atoms of TiCl.sub.4, TiBr.sub.4, Ti(CH.sub.3).sub.4,
etc., and a gas containing Cu atoms of bisacetyl acetonate copper Cu
(C.sub.5 H.sub.7 O.sub.2), bisdipivazoyl methanite copper Cu (C.sub.11
H.sub.19 O.sub.2).sub.2, bishexafluoroacetayl acetonate copper Cu (C.sub.5
HF.sub.6 O.sub.2).sub.2, or the like are properly combined and used as a
mixture gas atmosphere. Conductive materials such as Al-Si, Al-Ti, Al-Cu,
Al-Si-Ti, Al-Si-Cu, and the like are selectively deposited and an
electrode can be also formed.
The above Al-CVD method is a film forming method having an excellent
selectivity and the surface performance of the deposited film is good.
Therefore, by applying the non-selective film forming method to the next
depositing step and by also forming a metal film made of Al or containing
Al as a main component onto the above Al film which has selectively been
deposited and onto the insulating film of SiO.sub.2 and the like, the
suitable metal film having a high generality which is suitable as a wiring
of the semiconductor apparatus can be obtained.
Practically speaking, the following films can be used as such metal films:
that is, a combination of Al, Al-Si, Al-Ti, Al-Cu, Al-Si-Ti, and Al-Si-Cu
which have selectively been deposited and Al, Al-Si, Al-Ti, Al-Cu,
Al-Si-Ti, and Al-Si-Cu which have nonselectively been deposited; and the
like.
As a film forming method for the non-selective deposition, there are a CVD
method, a sputtering method, and the like other than the above-mentioned
Al-CVD method.
It is also possible to form a wiring in a manner such that a conductive
film is formed by a CVD method or a sputtering method and is patterned to
thereby form an underlaid layer having a desired wiring shape and, after
that, a metal film made of Al or containing Al as a main component is
selectively deposited onto the underlayer by using the Al-CVD method. In
this manner, a wiring is formed.
Further, a metal film can be also formed onto the insulative film by using
the Al-CVD method. For this purpose, a surface quality improving process
is executed to the insulative film and substantially the electron donative
surface portion is formed. At this time, if a pattern of a desired wiring
shape is drawn by using a beam, the metal film is deposited onto only the
electron donative portion of the wiring shape which has been drawn by the
selective deposition. Thus, a wiring can be formed in a self-aligning
manner without patterning.
The manufacturing steps of the photoelectric converting apparatus of the
structure of FIG. 6 have been described above. However, it will be
obviously understood that the photoelectric converting apparatuses of the
structures of FIGS. 5 and 7 can be easily obtained by omitting or changing
a part of the above manufacturing steps.
The invention is not limited to the foregoing BASIS sensor but can be also
similarly applied to photoelectric converting apparatuses of the type in
which photo carriers are accumulated onto the control electrode as shown
in, for instance, FIGS. 9 and 10. In FIG. 9, reference numeral 51 denotes
an MOS transistor; 52 a photodiode; and 53 an accumulation capacitor. In
FIG. 10, reference numeral 61 denotes an SIT and 62 indicates a capacitor.
Another embodiment of the invention will now be described with reference to
the drawings.
FIG. 11 is a schematic cross-sectional view for explaining another
embodiment. There is a difference between this embodiment and the
photoelectric converting apparatus which has already been described by
reference to FIG. 5. That is, in FIG. 1, the apparatus has a structure
such that the light shielding layer 1 and the transparent electrode 10 are
come into contact in the boundary region between the dark pixel D and the
light pixel L. On the other hand, in this embodiment, the transparent
electrode 10 formed over the light pixel L is extended until the region of
the dark pixel D.
By constructing the transparent electrode 10 so as to have a shape such
that it overlaps the region of the dark pixel D, it is possible to solve
the occurrence of the problem such that a necessary position cannot be
assured for the transparent electrode 10 because a positional deviation
occurs when the transparent electrode 10 is formed.
Although FIG. 11 shows an example in which the light shielding layer 1 and
the transparent electrode 10 partially overlap, the transparent electrode
10 can be also extended to a position on the light shielding layer 1 of
the regions of a plurality of dark pixels D.
For such an overlap structure, although the transparent electrode 10 has
been formed on the light shielding layer 1 in the diagram, the light
shielding layer 1 can be also laminated on the transparent electrode 10.
FIGS. 12 and 13 are schematic cross sectional views showing parts of the
photoelectric converting apparatuses corresponding to FIGS. 6 and 7,
respectively.
FIGS. 12 and 13 also differ from FIGS. 6 and 7 with respect to a point that
the light shielding layer 1 and the transparent electrode 10 are
overlappingly provided as described in FIG. 12.
FIGS. 12 and 13 also differ from FIGS. 6 and 7 with respect to a point that
only the light shielding layer 12 is formed on the device separating
region 3 as a boundary region between the light pixel and the dark pixel.
By using such a structure, since the portion on the boundary region is made
of a single material, not only the structure is simple but also the
photoelectric converting apparatus can be easily manufactured. In
addition, since a width of the boundary region can be also narrowed, the
above structure is also effective in terms of the space use efficiency and
the easiness of the design.
FIGS. 14 and 15 are schematic cross sectional views for explaining further
other embodiments of the invention, respectively. The embodiments are
modifications corresponding to the photoelectric converting apparatuses
shown in FIGS. 12 and 13, respectively.
In FIGS. 14 and 15, a light shielding layer 12' is also formed on the
boundary region of the pixel between the light pixels L and the
transparent electrode 10 is formed so as to overlap the light shielding
layer 12' between the light pixels.
As mentioned above, by also forming the light shielding layer 12' between
the light pixels, it is possible to prevent a problem such that in the
case where a photosignal or optical information has obliquely entered the
photosensitive surface of the photoelectric converting device, the light
enters the photo sensitive sections of the surplus photoelectric
converting devices.
Thus, in particular, a crosstalk between the light pixels can be reduced
and the capacity components of the dark pixel and the light pixel are made
coincide, so that the further accurate photoelectric conversion can be
accomplished.
FIGS. 16 and 17 are schematic cross-sectional views for explaining further
other embodiments of the invention, respectively.
The embodiments of FIGS. 16 and 17 differ from the foregoing embodiments
with respect to a point that the light shielding layer 1 formed on the
photoelectric converting device serving as a dark pixel is provided
through the transparent electrode 10.
By forming the light shielding layer 1 onto the transparent electrode 10 as
mentioned above, the patterning of the transparent electrode 10 becomes
unnecessary or easy, so that the yield can be improved and the costs can
be reduced.
In order to allow the function of the dark pixel to sufficiently operate,
it is effective to form the light shielding layer into the boundary region
between the light pixel and the dark pixel as shown in the diagrams. By
simultaneously having the light shielding layers 8 and 12' shown in Figs.
16 and 17, the incidence of the light into the photoelectric converting
device serving as a dark pixel can be further prevented.
The invention is not limited to the foregoing embodiments but it is
possible to combine each of the embodiments within the purview of the
spirit of the invention and many variations and modifications are also
included in the scope of the appended claims of the invention.
As described above, according to the photoelectric converting apparatuses
of the invention, the pixel acting as a light pixel is covered at a front
surface thereof by the transparent electrode having the same structure as
that of the light shielding layer for a dark pixel. Therefore, the
influences of the temporary accumulation capacitors or the like are
substantially equal with respect to the light pixel and the dark pixel and
the output of the dark pixel can be used as a stable black reference.
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